Plumes dimensions

Two of the more popular multicalculation software packages are FPETOOL (Nelson, 1990) and FASTLite (Portier, 1996). These two software packages contain more than a dozen fire protection calculation tools. They each also include a compartment fire model. The calculation tools are useful for obtaining first order approximations to fire-related aspects. The routines include vent flows, radiant heating of objects, sprinkler actuation, timed egress, and plume dimensions. Most of the tools are computerized versions of hand calculations and are useful in that capacity. 

In this expression, 3 represents the increase factor of vertical diffusion due to the plume. Gaussian plume or dispersion models are based on standard deviations of the plume dimensions (crx, cry, oz). These represent a measure of the diffusive capacity of the atmosphere. They are dependent on the turbulence conditions of the atmosphere, the vertical temperature gradient (which helps to establish atmospheric turbulence in the vertical direction) and the transporting distance. 

Figure 2.12 Characteristic dispersion mechanisms in canopies in the case of multiple buildings (see also Figure 2.3) On discrete/obstacle scale (for well-separated buildings, b/d 1) plume dimensions less than obstacle width.

The cloud/plume dimensions are functions of the wake turbulence and the distance downwind from theobstacle (x-x(kj) and travel time from detrainment i.e. At-Al(k). Their effective values at x = x(jt) + lw are determined by the scale of the wake, for... 

Note that the cloud/plume dimensions match each other at x = 0, y = xc in, where phase 3 becomes phase 4, so that... 

For a steady source, the structure of the resulting plume in the continuum region is primarily determined by its form in the boundary layer above the obstacles as given by (2.38), where aH s 1. On the continuum scale the value of (Uc) is only significant in determining the virtual origin and Arough surface, as discussed above. 

With such a model it is also necessary to estimate the effects on the cloud/plume dimensions of undulating terrain and any significant changes in stratification over the urban terrain. When, as is usual, the depth of the mixed layer, h, and Uh change over the diurnal period these expressions can be extended by using a FAM for the flow field and turbulence (as discussed in Section 2.2) and thence correcting the values of crx, time dependence should be considered especially when considering... 

Ao-x,Ao-y Increase in cloud/plume dimensions near a building ... 

Coordinates and plume dimensions relative to the mean streamline through the source (or through virtual sources), e.g. X ... 

Spreading of MTBE and Chlorinated Hydrocarbons in Groundwater Comparison of Groundwater Transport and Plume Dimensions... 

As we noted in Section 18.7, the variances of the mean plume dimensions can be expressed in terms of the motion of single particles released from the source. (At a particular instant the plume outline is defined by the statistics of the trajectories of two particles released simultaneously at the source. We have not considered the two-particle problem here.) In an effort to overcome the practical difficulties associated with using (18.72) to obtain results for Gy and gz, Pasquill (1971) suggested an alternate definition that retained the essential features of Taylor s statistical theory but that is more amenable to parametrization in terms of readily measured Eulerian quantities. As adopted by Draxler (1976), the American Meteorological Society (1977), and Irwin (1979), the Pasquill representation leads to... 

Dispersion A hydrologic process which affects mixing of solutes at the grain scale owing to differences in flow path, and rates, which tend to elongate and broaden contaminant plume dimensions. 

The geometrical relationships between the laser beam, plume, target, and MBMS sampling axis are shown, to scale, in more detail in Figure 3. The plume dimensions shown are based on images [4] obtained at early times in the expansion of ionized A1 (Al" produced by 248 nm KrF excimer laser interaction ( 30 ns pulse) with... 

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